Scielo RSS<![CDATA[Revista mexicana de física]]>
http://www.scielo.org.mx/rss.php?pid=0035-001X20190005&lang=en
vol. 65 num. 5 lang. en<![CDATA[SciELO Logo]]>http://www.scielo.org.mx/img/en/fbpelogp.gif
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<![CDATA[The Higgs profile in the standard model and beyond]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500419&lng=en&nrm=iso&tlng=en
Abstract We present a review of Higgs physics in the SM and beyond, including the tests of the Higgs boson properties that have been performed at LHC and have permitted to delineate its profile. After presenting the essential features of the Brout-Englert-Higgs (BEH) mechanism, and its implementation in the SM, we discuss how the Higgs mass limits developed over the years. These constraints, in turn, helped to classify the Higgs phenomenology (decays and production mechanisms), which provided the right direction to search for the Higgs particle, an enterprise that culminated with its discovery at LHC. So far, the constraints on the couplings of the Higgs particle, point towards an SM interpretation. However, the SM has open ends that suggest the need to look for extensions of the model. We discuss in general the connection of the Higgs sector with some new physics (e.g. supersymmetry, flavor and Dark matter), with special focus on a more flavored Higgs sector. This is realized in the most general 2HDM, and its textured version, which we study in general, and for its various limits, which contain distinctive flavor-violating signals that could be searched at current and future colliders.<![CDATA[Rapid monitoring of heavy metals in fluvial sediments using laser-induced breakdown spectroscopy]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500440&lng=en&nrm=iso&tlng=en
Abstract In this work, a quantitative analysis of heavy metals Cr and Cu in fluvial sediments was carried out by Laser-induced breakdown Spectroscopy (LIBS) to assess the anthropogenic. To perform the analysis, different sediment samples were collected at selected positions. Standard addition calibration curves were constructed for Cr and Cu by measuring the Cr I line at 357.87 nm and Cu I line at 324.75 nm. The moisture and organic matter contents of the sediments were taken into account to overcome the matrix effect. The quantitative models were evaluated statistically to evaluate the robustness and prediction ability of the method. Low values for root-mean-square errors for calibration (RMSEC), prediction (RMSEP) and cross-validation (RMSECV) were calculated. High values of the correlation coefficients of calibration ( R 2 c = 0:984 for Cr; R 2 c = 0:986 for Cu) and cross-validation ( R 2 c v = 0:985 for Cr; R 2 c v = 0:981 for Cu) were obtained. The calculated limits of detection (LoD) were 2.9 ppm for Cr and 3.3 ppm for Cu, and the limits of quantification (LoQ) were 9.5 ppm for Cr and 11 ppm for Cu. Concentrations of Cr and Cu higher than the baseline values were obtained in the sediments downstream (Cr: 49 ppm, Cu: 81 ppm) which are indicative of the pollution of the basin by heavy metals due to the spill of untreated effluents derived from anthropogenic activities. LIBS analysis was optimized for reliable heavy metal monitoring in fluvial sediments.<![CDATA[Raman spectroscopic study of the influence of voltage-time on titania growth-fast anodized nanostructures]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500449&lng=en&nrm=iso&tlng=en
Abstract TiO2 nanotubes were prepared by the anodization process of a set of titanium foils in order to study the influence of time and voltage on the morphology of them under a 1.2 wt % NH4F salt concentration, taking advantage of this percent and remarking the great importance of the oxide growth-dissolution speed with this electrolyte concentration. The anodization process consists of an organic media of ethylene glycol, a voltage from 5 to 30 V for a time period from 1 to 6 hours, a constant potential of 30 V for a time lapse from 10 to 360 minutes and 5 to 480 seconds. All anodized samples are rinsed and annealed to 400 ° C for 3 hours to obtain an anatase crystalline structure. The morphological characterization was carried out by Field Emission Scanning Electron Microscopy (FESEM) to verify the presence of the main nanostructures: nanopores, nanotubes, and nanograss. Raman spectroscopy was used for optical characterization in order to identify the changes in the signal of the E g (v6) vibrational mode. It was observed the Raman E g (v6) vibrational mode suffers a redshift at the initial anodization stage with the contribution of the stress between the substrate-oxide layer and the stoichiometry defects. The diameter and tube length have a strong correlation with the oxide thickness (ascendant slope), moreover, this oxide is compared and related to the Raman intensity of the E g (v6) mode, from this fact, it is easy to define some time periods and a voltage range for each titania nanostructures observed.<![CDATA[Structural and optical characterization of the crystalline phase transformation of electrospinning TiO<sub>2</sub> nanofibres by high temperatures annealing]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500459&lng=en&nrm=iso&tlng=en
Abstract The electrospinning technique has been used to synthesize TiO2 nanofibres, which by annealing at high temperatures achieves the crystalline phase transformation of anatase to rutile passing through the anatase-rutile mixed. The investigated temperature range was 0-1000 ° C. The TiO2 nanofibres surface morphology and chemical stoichiometry were obtained by Scanning Electron Microscopy and Energy Dispersive Spectrometry. The annealed nanofibres diameter was ranged from 137.0 to 115.3 nm in the investigated temperature range. The influence of the annealing temperature on the structure and crystalline phase quality of the TiO2 nanofibres has been investigated by X-ray diffraction and Raman scattering. Clear evidence have been obtained of the structural transformation of TiO2 nanofibres from pure anatase to pure rutile, including the almost amorphous and anatase-rutile mixed structural phases by X-ray diffraction and confirmed by Raman scattering. By X-ray diffraction was found that the TiO2 nanofibres crystalline phases presented as preferential growth direction (101) for anatase and (110) for rutile. The Raman spectroscopy exhibits the anomalous behavior for band broadening and shifting of Raman bands with increasing crystallite size that forms the nanofibres. The room-temperature photoluminescence presents radiative bands whose dominant band redshifts from 2.56 to 1.32 eV, as the crystalline phase is transformed by annealing at high temperature.<hr/>Resumen La técnica de electrohilado se ha utilizada para sintetizar nanoﬁbras de TiO2, que al recocerlas a altas temperaturas se logra la transformación de la fase cristalina de anatasa a rutilo pasando a través de la mezcla anatasa-rutilo. El rango de temperatura investigado fue de 0 a 1000°C. La morfología superﬁcial y la estequiometria química de las nanoﬁbras de TiO2 se obtuvieron mediante microscopía electrónica de barrido y espectrometría de dispersión de energía. El diámetro de las nanoﬁbras recocidas osciló entre 137.0 a 115.3 nm en el rango de temperatura investigado. La inﬂuencia de la temperatura de recocido en la estructura y la calidad de la fase cristalina de las nanoﬁbras de TiO2 ha sido investigada mediante difracción de rayos X y dispersión Raman. Se han obtenido evidencias claras de la transformación estructural de nanoﬁbras de TiO2 desde anatasa pura a rutilo puro, incluidas las fases estructurales casi amorfas y mezcla anatasa-rutilo mediante difracción de rayos X y conﬁrmada por dispersión Raman. Por difracción de rayos X se encontró que las fases cristalinas de las nanoﬁbras de TiO2 presentaron como dirección de crecimiento preferencial (101) para la anatasa y (110) para el rutilo. La espectroscopia Raman muestra el comportamiento anómalo para el ensanchamiento y desplazamiento de las bandas de Raman a medida que aumenta el tamaño de los cristales que forman las nanoﬁbras. La fotoluminiscencia a temperatura ambiente presenta bandas de radiación cuya cuya banda dominante se desplazada al rojo desde 2.56 a 1.32 eV, a medida que la fase cristalina se transforma por efecto del recocido a alta temperatura.<![CDATA[Ab initio investigation of the electronic structure, elastic and magnetic properties of quaternary Heusler alloy Cu<sub>2</sub>MnSn <sub><em>1-x</em></sub> In <sub><em>x</em></sub> (<em>x</em> = 0<em>,</em> 0<em>.</em>25<em>,</em> 0<em>.</em>5<em>,</em> 0<em>.</em>75<em>,</em> 1)]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500468&lng=en&nrm=iso&tlng=en
Abstract Structural, elastic, electronic and magnetic properties of the quaternary Heusler alloys Cu2MnSn 1-x In x (x = 0, 0.25, 0.5, 0.75, 1) are calculated using the full-potential linearized augmented plane wave (FP-LAPW) method in the framework of the density functional theory (DFT) and implemented in WIEN2k code. The exchange-correlation potential is evaluated using the generalized gradient approximation (GGA) within the Perdew-Burke-Ernzerhof (PBE) parameterization. Our theoretically results provide predictions for the mixed Cu2MnSn 1-x In x in which no experimental and theoretical data are currently available. The lattice parameter and bulk modulus as well the elastic constants and their related elastic moduli for Cu2MnSn 1-x In x have been calculated. Also, the electronic properties including density of states and band structures indicate the metallic character for Cu2MnSn 1-x In x . Morever, this quaternary Heusler alloy is found to be ferromagnetic, brittle and anisotropic in nature.<![CDATA[A new ordered vacancy compound; preparation and crystal structure of Ag<sub>3</sub>In<sub>5</sub>□Te<sub>9</sub>]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500475&lng=en&nrm=iso&tlng=en
Abstract The new ordered vacancy compound Ag3In5□Te9 was synthesized by the melt and annealing technique and its structure was refined from X-ray powder diffraction pattern using the Rietveld method. The title compound crystallizes in the tetragonal space group P 4 -2c(N ° 112), with a = 6.3453(2) Å, c = 12.5754(7) Å, V = 506.32(4) Å 3. The refinement of 23 instrumental and structural parameters led to Rp = 5.4%, Rwp = 5.8%, Rexp = 5.1%, S = 1.1. This ternary compound is isostructural with Cu3In5□Te9 and have a defect adamantane structure.<![CDATA[On Cattaneo-Christov heat flux analysis with magneto-hydrodynamic and heat generation effects in a Carreau nano-fluid over a stretching sheet]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500479&lng=en&nrm=iso&tlng=en
Abstract This pagination specifies the characteristics of Cattaneo-Christov heat diffusion model for the stagnation point flow of a Carreau nano-fluid. The momentum equation is manifested with magneto-hydrodynamic effect and the generalised Fourier’s law and Fick’s law are considered to manipulate the heat and mass flux with heat generation and chemical reaction. The fluid flow having infinite shear rate viscosity is caused by the stretched sheet. The admissible transformations are invoked to alter the flow narrating coupled partial differential system into the coupled ordinary differential system. Later on, these equations are sorted out numerically with the aid of Runge-Kutta Fehlberg method supported with shooting scheme. The graphs are plotted that portrays the impact of fluid velocity and temperature towards various engineering parameters which reveals that the fluid temperature increases when enlarging heat generation parameter. The validations for the numerical values of skin friction coefficient are delineated with the existing literature. Also, the numerical findings for the local Nusselt number are offered.<![CDATA[Determining the gravitational effects on tide height on an estuary and theoretical comparisons]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500489&lng=en&nrm=iso&tlng=en
Abstract Two identical homemade prototypes are used to monitoring the tide levels on two strategic points of the Serinhaém estuary. This monitoring was realized along a period close to the new moon phase. From the analysis of the experimental results, the average height of the tide is determined between each period of high-tide and low-tide. These estimations show discrepancies minors than half order of magnitude, compared to the theoretical predictions of the static and dynamic oceanic tide models. Also, the amplification effects of the tide in the estuary head can be quantified exhibiting a maximum gain of 1.33, which is observed in the new moon phase.<![CDATA[Magnetic motion of spherical frictional charged particles on the unit sphere]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500496&lng=en&nrm=iso&tlng=en
Abstract Mathematically, the unit sphere 𝕊2 is described in an ordinary space with positive curvature. In this study, we aim to present the manipulation of a spherical charged particle in a continuous motion with a magnetic field on the sphere 𝕊2 while it is exposed to a frictional force. In other words, we effort to derive the exact geometric characterization for the spherical charged particle under the influence of a frictional force field on the unit 2-sphere. This approach also helps to discover some physical and kinematical characterizations belonging to the particle such as the magnetic motion, the torque, the potential energy functional, and the Poynting vector.<![CDATA[The generalized exponential rational function method for Radhakrishnan-Kundu-Lakshmanan equation with <em>β</em>-conformable time derivative]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500503&lng=en&nrm=iso&tlng=en
Abstract In this paper, the generalized exponential rational function method is used to construct exact solutions of the β conformable-time Radhakrishnan-Kundu-Lakshmanan equation. This model governs soliton propagation dynamics through a polarization-preserving fiber. Fractional derivatives are described in the β-conformable sense. As a result, we get new form of solitary traveling wave solutions for this model including novel soliton, traveling waves and kink-type solutions with complex structures. Physical interpretations of some extracted solutions are also included through taking suitable values of parameters and derivative order in them. It is proved that this method is powerful, efficient, and can be fruitfully implemented to establish new solutions of nonlinear conformable-time partial differential equations applied in mathematical physics.<![CDATA[Asymptotically equivalent functions and ultrafilters applied to noncommutative quantum cosmology]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500519&lng=en&nrm=iso&tlng=en
Abstract Using the semi-classical approximation to the Wheeler-DeWitt equation obtained via Arnowitt-Deser-Misner (ADM) formalism in the Friedmann-Lemaȋtre-Robertson-Walker (FLRW) model coupled to a scalar field with positive cosmological constant in the Kantowski-Sachs (KS) Universe, we introduced a deformation on the commutation relation for the minisuperspace variables and find an explicit semiclassical expression equivalent, in an adequate limit, to the solution with the aid of asymptotically equal functions and the theory of Ultrafilters, offering a suggestive alternative to sketch the behavior of the dynamical system involved without the need to solve it numerically.<![CDATA[Symmetry properties and exact solutions of the time fractional Kolmogorov-Petrovskii-Piskunov equation]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500529&lng=en&nrm=iso&tlng=en
Abstract In this paper, the time fractional Kolmogorov-Petrovskii-Piskunov (TFKPP) equation is analyzed by means of Lie symmetry approach. The TFKPP is reduced to ordinary differential equation of fractional order via the attained point symmetries. Moreover, the simplest equation method is used in construct the exact solutions of underlying equation with recently introduced conformable fractional derivative.<![CDATA[New reflections on higher dimensional linearized gravity]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500536&lng=en&nrm=iso&tlng=en
Abstract We make a number of remarks on linearized gravity with cosmological constant in any dimension, which, we argue, can be useful in a quantum gravity framework. For this purpose we assume that the background space-time metric corresponds to the de Sitter or anti-de Sitter space. Moreover, via the graviton mass and the cosmological constant correspondence, we make some interesting observations, putting special attention on the possible scenario of a graviton-tachyon connection. We compare our proposed formalism with the Novello and Neves approach.<![CDATA[Neutron and gamma-ray fluxes measured by SciCRT prototype at the top of sierra negra volcano, Mexico]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500545&lng=en&nrm=iso&tlng=en
Abstract The mini-SciCR is a cosmic ray detector, made of scintillator bars with a total volume of 20 × 20 × 20:8 cm3. The array of scintillator bars act both as a target and as a tracker of the incident radiation. In this paper we describe the method developed with the help of a Monte Carlo simulation to distiguish the neutron signals from gamma ray signals, which is based on the different maximum energy deposited at a scintillator bar by neutrons and gamma rays. To distiguish the neutral emission signals (neutrons and gamma rays) from charged particles signals, we implemented via software a system of anti-coincidence between edge bars and internal bars of the detector. We also report the flux of neutrons and gamma rays measured by the mini-SciCR at the top of the Sierra Negra volcano at 4,600 m.a.s.l., in Eastern Mexico. The mini-SciCR was operating from October 2010 to July 2012. We also present the Forbush decrease registered by the mini-SciCR on march, 2012. The mini-SciCR is a prototype of a new cosmic ray detector called SciBar Cosmic Ray Telescope installed in the same place, which is in the process of operation parameter tuning and calibration. The SciCRT will work mainly as a Solar Neutron and Muon Telescope.<![CDATA[The role of SnO<sub>2</sub> high resistivity transparent layer deposited onto commercial conducting glass as front contact in superstrate configuration thin films solar cells technology: influence of the deposition technique]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500554&lng=en&nrm=iso&tlng=en
Abstract The deposition of a High Resistivity Transparent oxide between a Transparent Conductive Oxide and the window Cadmium sulfide has demonstrated the improvement of performance of Cadmium sulfide/Cadmium telluride solar cells, fabricated in the superstrate-configuration. In this work the influence of the Pneumatic Spray Pyrolysis and magnetron sputtering techniques on the properties TCO/SnO2/CdS structure through the deposition of the intermediate SnO2 between the commercial conducting glass and CdS window is presented by means of X-ray Photoelectron Spectroscopy, Secondary Ion Mass Spectroscopy, and contact resistance, calculated using Transmission Line Method, in order to reduce the front contact resistance in devices with superstrate-configuration. The results of this work are applicable to other solar cells in the same configuration as the recent solar cells based on the compound Sb2Se3, where the use of this type of High Resistivity Transparent has not been studied.<![CDATA[Design and construction of a single-axis, low-frequency magnetic probe (<em>B</em>-dot probe) calibrated with a <em>LC</em> <sub><em>var</em></sub> Helmholtz resonant circuit]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500560&lng=en&nrm=iso&tlng=en
Abstract Magnetic probes (also known as B-dot coil) are electromagnetic devices used to measure magnetic field variations in many frequency ranges. The measured magnetic field frequency directly relates to the elected method to make the B-dot coil calibration. This work presents a B-dot coil calibration in a frequency range from 6.16 kHz to 36.63 kHz. An inductor L (Helmholtz coil) connects in parallel with a variable capacitor bank C var to form a coupled LC var resonant circuit. The LC var circuit is fed with a half bridge oscillator. The capacitance C var is varied until the circuit is in a resonant state at different frequencies. The resonant circuit produces sinusoidal oscillations in the aforementioned frequency band. The sensitivity is calculated by using voltage V out of the B-dot coil and voltage V H measured from Helmholtz terminals.<hr/>Resumen Las sondas magnéticas (también conocidas como bobinas de punto B) son dispositivos electromagnéticos utilizados para medir la variación del campo magnético en muchos rangos de frecuencia. La frecuencia del campo magnético a medir se relaciona directamente con el método elegido para realizar la calibración de la bobina de punto B. Este trabajo presenta una calibración de bobina de punto B en un rango de frecuencia de 6.16 kHz a 36.63 kHz. Un inductor L (bobina de Helmholtz) se conecta en paralelo con un banco de condensadores variable C var para formar un circuito resonante LC var acoplado. El circuito LC var se alimenta con un oscilador de medio puente. La capacidad C var varía hasta que el circuito se encuentra en estado resonante a diferentes frecuencias. El circuito resonante produce oscilaciones sinusoidales en la frecuencia de banda mencionada. La sensibilidad se calcula utilizando el voltaje V out de la bobina de punto B y el voltaje V H medido desde las terminales de Helmholtz.<![CDATA[Extracting fairly accurate proton range formulas for use in microdosimetry]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500566&lng=en&nrm=iso&tlng=en
Abstract Radiation therapy is a promising treatment for cancer patients. The highest dose of radiation must be deliver to tumor and the lowest to the healthy tissues. Since charged particles such as protons have high stopping-power at track-end, these particles can be used to treat tumors close to sensitive tissues. Formulas that commonly used for proton stopping-power in a soft tissue-equivalent (T.E.) material and each of its elements have 48 and 12 constants respectively. Due to the complexity of formulas, high number of constants, high occupancy of computer memory, and rounding error of computer, existing formulas reduces information processing speed. Because of the importance of proton therapy and its applications in dosimetry, microdosimetry, detectors, and computer simulations of these systems, it is necessary to use fast and accurate formulas for the stopping-power and range in the T.E., and its elements. We wrote a computer code in FORTRAN programming language, and used the fitting method and obtained simple and fairly accurate formulas for the proton range in these materials. Our range formulas in T.E. have 6 constants, and this formulas in elements of T.E. include carbon, nitrogen, and oxygen have 4 and hydrogen have 8 constants. So our formulas greatly reduce the above mentioned errors.<![CDATA[A comprehensive analysis of <sup>9</sup>Li + <sup>70</sup>Zn fusion cross section by using proximity potentials, temperature dependent density distributions and nuclear potentials]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500573&lng=en&nrm=iso&tlng=en
Abstract The fusion cross section of 9Li + 70Zn reaction is studied in an extensive manner within the framework of different theoretical approaches. For this purpose, three different methods which consist of proximity potentials, temperature dependent densities and temperature dependent nuclear potentials are used in order to determine the real part of the nuclear potential. The imaginary part is considered as Woods-Saxon potential. The calculated fusion cross sections are compared with the experimental data. The theoretical results describe the experimental data very well. It is seen that the applied approaches are different ways to study the reactions involving fusion cross sections.<![CDATA[Shearography as a tool to measure creep strain in sealing elastomers]]>
http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2019000500583&lng=en&nrm=iso&tlng=en
Abstract In this work, an application of digital speckle pattern shearing interferometry (shearography) for strain measurement is proposed. This optical technique is implemented to measure strain in elastic materials. Three different sealing elastomers were tested in short-term creep tests in order to assess creep compliance, which is an important mechanical property for viscoelastic materials. The creep tests were carried out applying a constant tensile load to a specimen. An in-plane shearography setup was implemented to measure the creep strains in polymers. Results of creep strains were compared with that obtained with a commercial equipment of digital image correlation (DIC). Although some limitations were found for shearography, it was possible to verify the adaptability of this technique for strain measurement in elastomers.